Gallium nitride compound semiconductor light emitting device and

Details Gallium nitride compound semiconductor light emitting device and Gallium nitride compound semiconductor light emitting device and

1997-09-19

2000-12-26

Chaudhuri, Olik

Semiconductor device manufacturing: process

Making device or circuit emissive of nonelectrical signal

Compound semiconductor

117 89, H01L 2100

Patent

active

06165812&

DESCRIPTION:

BRIEF SUMMARY
TECHNICAL FIELD

The present invention relates to a gallium nitride group compound semiconductor light-emitting element which emits light in a range from a blue region to an ultraviolet region, and also relates to a method for producing gallium nitride group compound semiconductor used for such a light-emitting element.


BACKGROUND ART

Light-emitting elements which emit light in a wavelength region having a wavelength shorter than that of blue light are expected to be applied as light sources for full-color displays, optical disks on which recording can be performed at a high density, and the like. As the semiconductors usable for such light-emitting elements, Group II-VI compound semiconductors such as ZnSe and Group III-V compound semiconductors such as SiC and GaN are known and have been researched vigorously. Recently, a blue-light-emitting diode was realized by using compound semiconductors such as GaN and In.sub.x Ga.sub.1-x N (where 0<x<1, hereinafter, simply referred to as "InGaN"). Thus, light-emitting elements using gallium nitride group compound semiconductors have recently been the object of particular attention (see Japanese Laid-Open Publication No. 7-162038).
Hereinafter, a conventional gallium nitride group compound semiconductor light-emitting element will be described with reference to FIG. 19. This light-emitting element includes a multi-layer structure including: GaN buffer layer 101; an n-type Al.sub.x Ga.sub.1-x N (where 0<x<1, hereinafter, simply referred to as "AlGaN") cladding layer 102; an InGaN active layer 103; a p-type AlGaN cladding layer 104; and a p-type GaN contact layer 105, these layers having been sequentially stacked in this order on a sapphire substrate (made of single crystalline Al.sub.2 O.sub.3) 100. A p-side electrode (Au electrode) 107 is formed on the p-type GaN contact layer 105. An n-side electrode 108 (Al electrode) is formed on an exposed part of the n-type AlGaN cladding layer 102.
Hereinafter, a method for producing gallium nitride group compound semiconductor to be used for a conventional light-emitting element will be described with reference to FIGS. 20(a) to 20(d).
Gallium nitride group compound semiconductors are generally formed by a metalorganic vapor phase epitaxy (MOVPE) method or a molecular beam epitaxy (MBE) method. Herein, an exemplary method for producing gallium nitride group compound semiconductor using the MOVPE method will be described.
First, a sapphire substrate (made of single crystalline A.sub.2 O.sub.3) 121 such as that shown in FIG. 20(a) is placed in the reactor of an MOVPE apparatus (not shown). Then, an organic metal such as trimethylgallium (TMG) and ammonium (NH.sub.3) are supplied onto the substrate 121 at a temperature of about 600.degree. C. while using hydrogen as a carrier gas, thereby depositing a polycrystalline GaN layer 122a on the substrate 121.
Next, a single crystalline GaN layer is formed on the polycrystalline GaN layer 122a. FIG. 2(b) illustrates a growth sequence of a single crystalline GaN layer. Hereinafter, this process step will be described in more detail.
After the supply of TMG as the material of Ga is suspended and the temperature of the substrate 121 has been raised to about 1000.degree. C., TMG is supplied again onto the substrate. As a result, nuclei 122b of GaN single crystals showing a high degree of alignment along the crystal axes are formed as shown in FIG. 20(b). The grain size of the nuclei 122b of the GaN single crystals which are formed at such a temperature (of about 1000.degree. C.) is in the range from about several .mu.m to about several hundred .mu.m.
Next, when TMG and NH.sub.3 are continuously supplied while maintaining the temperature of the substrate 121 at about 1000.degree. C., the nuclei 122b of the GaN single crystals grow principally in a two-dimensional manner, as shown in FIG. 20(c). As a result, the nuclei 122b come into contact with each other, thereby forming a single crystalline GaN layer 122c as shown in FIG. 20(d). The polycrystalline GaN layer 122a and the

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Akihiko Ishibashi et al., MOVPE Growth Of High Quality GaN/InGaN Single Quantum Well Structure Using Misoriented SiC Substrate, Extended Abstracts of the 1996 International Conference on Solid State Devices and Materials, Yokohama, Sympo. V-8, 1996, pp. 79-81.

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